CH^ENAXIS. 3 



situated as usual, the lower palatal a little more deeply placed 

 and longer than the others, and there is often a small inter- 

 palatal denticle. There is no supracolumellar lamella. 



Length 3.3, diam. 1.6 mm. (original figure, and pi. 9, fig. 1). 



Length 3, diam. 1.5 mm. (smallest in type lot). 



Arizona: Drift debris of the San Pedro Kiver, one mile 

 east of Benson (type locality; Ferriss and Pilsbry) ; near 

 Dos Cabezas Cave, west of the Dos Cabezas Range, Cochise 

 Co. (Mort Wien) ; Tumamoc Hill, under stones, and in flood 

 debris at the west end of Congress St., Tucson (Pilsbry and 

 Ferriss) . 



Bifidaria tuba P. & F., Proc. A. N. S. Phila., 1906, p. 145 ; 

 fig. 6; 1910, p. 144; 1915, p. 390. 



This species lives in the arid foothills and low mountains 

 of the Lower Sonoran zone, not in the higher mountains. It 

 is rare in the debris of the San Pedro River, probably washed 

 in from the foothills of the Whetstone Mountains, or possibly 

 the hill country about Tombstone. 



A few specimens were found under stones on Tumamoc 

 Hill, and more, together with C. intuscostata, in flood debris 

 at the foot of the hills at the west end of Congress St., Tucson. 

 These specimens have a small supracolumellar nodule, some- 

 times two (pi. 9, fig. 3), but no spiral lamella running in- 

 ward from it, though there is a shallow spiral depression, 

 scarcely to be called a furrow, on the internal axis. 



2. CH^NAXIS INTUSCOSTATA (Clapp). PL 9, figs. 6 to 9. 



The shell is openly umbilicate, cylindric, usually longer 

 than C. tuba, and composed of about 6% whorls ; light brown. 

 Last whorl, aperture and teeth as in C. tuba, but the supra- 

 columellar lamella is almost invariably present and visible 

 from in front, and the subcolumellar nodule is conspicuous. 

 Inside there is a strong, cord-like lamella about 1% to 2 

 whorls long, terminating near and behind the supracolumel- 

 lar nodule. 



Length 3.85, diam. 1.65 mm.; 6% whorls (fig. 9). 



" Length 4.2, diam. 2 mm.; 6% whorls (largest )." 



